imx: imx_csu: Add a simple CSU layer

- Add a header to define imx_csu_init().
- Defines the Central Security Unit's Config Security Level
  permission bits.
- Define CSU_CSL_OPEN_ACCESS permission bitmask
- Run a loop to setup peripheral CSU permissions
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>

plat/imx/common/imx_csu.c

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include <mmio.h>
+#include <imx_csu.h>
+#include <imx_regs.h>
+
+void imx_csu_init(void)
+{
+	int i;
+	uintptr_t *csl_reg = (uintptr_t *)CSU_BASE;
+
+	for (i = 0; i < MXC_MAX_CSU_REGS; i++, csl_reg++)
+		mmio_write_32((uintptr_t)csl_reg, CSU_CSL_OPEN_ACCESS);
+}

plat/imx/common/include/imx_csu.h

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#ifndef __IMX_CSU_H__
+#define __IMX_CSU_H__
+
+#include <arch.h>
+
+/*
+ * Security Reference Manual for i.MX 7Dual and 7Solo Applications Processors,
+ * Rev. 0, 03/2017 Section 3.3.1
+ *
+ * Config secure level register (CSU_CSLn)
+ */
+#define CSU_CSL_LOCK_S1		BIT(24)
+#define CSU_CSL_NSW_S1		BIT(23)
+#define CSU_CSL_NUW_S1		BIT(22)
+#define CSU_CSL_SSW_S1		BIT(21)
+#define CSU_CSL_SUW_S1		BIT(20)
+#define CSU_CSL_NSR_S1		BIT(19)
+#define CSU_CSL_NUR_S1		BIT(18)
+#define CSU_CSL_SSR_S1		BIT(17)
+#define CSU_CSL_SUR_S1		BIT(16)
+#define CSU_CSL_LOCK_S2		BIT(8)
+#define CSU_CSL_NSW_S2		BIT(7)
+#define CSU_CSL_NUW_S2		BIT(6)
+#define CSU_CSL_SSW_S2		BIT(5)
+#define CSU_CSL_SUW_S2		BIT(4)
+#define CSU_CSL_NSR_S2		BIT(3)
+#define CSU_CSL_NUR_S2		BIT(2)
+#define CSU_CSL_SSR_S2		BIT(1)
+#define CSU_CSL_SUR_S2		BIT(0)
+
+#define CSU_CSL_OPEN_ACCESS  (CSU_CSL_NSW_S1 | CSU_CSL_NUW_S1 | CSU_CSL_SSW_S1 |\
+			      CSU_CSL_SUW_S1 | CSU_CSL_NSR_S1 | CSU_CSL_NUR_S1 |\
+			      CSU_CSL_SSR_S1 | CSU_CSL_SUR_S1 | CSU_CSL_NSW_S2 |\
+			      CSU_CSL_NUW_S2 | CSU_CSL_SSW_S2 | CSU_CSL_SUW_S2 |\
+			      CSU_CSL_NSR_S2 | CSU_CSL_NUR_S2 | CSU_CSL_SSR_S2 |\
+			      CSU_CSL_SUR_S2)
+void imx_csu_init(void);
+
+#endif /* __IMX_CSU_H__ */